Some types of partial middle ear implantable (P-MEI), total middle ear implantable (T-MEI), cochlear implant, or other hearing assistance systems utilize components disposed within the middle ear or inner ear regions. Such components may include an input transducer for receiving sound vibrations or an output stimulator for providing mechanical or electrical output stimuli based on the received sound vibrations.
An example of one such device is disclosed in U.S. Pat. No. 4,729,366, issued to D. W. Schaefer on Mar. 8, 1988. In the '366 patent, a mechanical-to-electrical piezoelectric input transducer is associated with a malleus bone in the patient's middle ear. The malleus vibrates in response to sounds received at the patient's tympanic membrane (eardrum). The piezoelectric input transducer transduces a mechanical energy of the malleus vibrations into an electrical signal, which is amplified and further processed by an electronics unit. A resulting electrical signal is provided to an electrical-to-mechanical piezoelectric output transducer that generates a mechanical vibration that is coupled to a stapes bone in the ossicular chain or to an oval window or round window of a cochlea. In the '366 patent, the ossicular chain is interrupted by removal of an incus bone. Removal of the incus prevents the mechanical vibrations delivered by the piezoelectric output transducer from mechanically feeding back to the piezoelectric input transducer.
Piezoelectric transducers are one example of a class of electromechanical transducers that require contact to sense or provide mechanical vibrations. For example, the piezoelectric input transducer in the '366 patent contacts the malleus for detecting mechanical vibrations. In another example, the piezoelectric output transducer in the '366 patent contacts a stapes bone or the oval or round window of the cochlea.
Proper positioning of the transducer and good contact between the transducer and the malleus is essential to properly transducing the received mechanical vibrations into a resulting electrical signal for hearing assistance processing. For example, there is a need in the art to ascertain whether too much force between the transducer and the malleus can mechanically load the vibrating malleus and attenuate the desired mechanical vibration signal or alter its frequency characteristics. It may be likely that, in an extreme case, too much force can damage or break either the malleus or the transducer. It may also be likely that too little force between the transducer and the malleus may be insufficient to detect the mechanical vibration signal, and is more likely to result in a complete loss of signal detection if the transducer and the malleus become dissociated.
Good contact between the transducer and the stapes is also critical for assisting hearing by providing mechanical stimulation. For example, there is a need in the art to ascertain whether too much force between the stimulating transducer and the stapes can attenuate the mechanical vibration signal provided by the transducer or alter its frequency characteristics. It may be likely that, in an extreme case, too much force can damage or break either the stapes or the transducer. It may also be likely that too little force between the stimulating transducer and the stapes may be insufficient to vibrate the stapes, and is more likely to result in a complete loss of assisted mechanical vibrations if the stimulating transducer and the stapes become dissociated. There is a need in the art to better control contact between the transducer and an auditory element such as the malleus or the stapes.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for improved transducer positioning and contact to an auditory element while sensing and providing middle ear sound vibrations.